1. Technical Field
The present invention relates to display devices.
2. Description of the Related Art
In recent years, demand for display devices in mobile devices such as cellular phones and electronic paper has been increasing. In a display device, a single pixel includes a plurality of sub pixels and the sub pixels each emit light in colors different from one another, and by switching the display of the respective sub pixels on and off, various colors are displayed with one pixel. In such a display device, display characteristics such as resolution and luminance have been improved year after year. However, as the resolution becomes higher, a numerical aperture decreases. Hence, there are problems in that it needs to increase the luminance of a backlight when trying to achieve high luminance, and whereby the power consumption of the backlight increases. To improve the situation, there has been a technology that adds white pixels that are the fourth sub pixel, in addition to the conventional sub pixels of red, green, and blue (see Japanese Patent Application Laid-open Publication No. 2011-154323 (JP-A-2011-154323)). This technology decreases the value of current for the backlight as much as the white pixels improve the luminance, and thus reduces the power consumption. When the value of current for the backlight is not decreased, because the luminance is improved by the white pixels, by using this, the visibility under the outdoor daylight can be improved.
The technology disclosed in JP-A-2011-154323 describes a display device that includes an image display panel composed of pixels each composed of a first sub pixel, a second sub pixel, a third sub pixel, and a fourth sub pixel and arrayed in a two-dimensional matrix, and a signal processor that receives an input signal and outputs an output signal. In JP-A-2011-154323, FIGS. 2, 22, and 23 illustrate the arrays of the first sub pixels, the second sub pixels, the third sub pixels, and the fourth sub pixels. In the pixel arrays disclosed in JP-A-2011-154323, however, the numerical aperture may be reduced as pixel density becomes higher.
For the foregoing reasons, there is a need for a display device in which first sub pixels, second sub pixels, third sub pixels and fourth sub pixels are arranged and in which pixel density cam become higher.